There are many factors that could contribute to heavy steering:
Tyre width - tyre brand/type - tyre pressure - wheel offset - alignment, etc
I have also found that old tyres (harder rubber-less tread flex) give stiffer steering.
 
"I think the popular Nissan GTR and GTST's have 32mm ??"
 
GTR 16x8" (rears) has 30mm offset and GTST 16x7 (front) has 40mm offset.
 
With the GTST, offset is close to the stock 45mm, and if you were to run a 205/50R16 tyre (many people do) it would have a slightly larger rolling diameter that would take it effectively even closer to stock as far as scrub radius is concerned meaning lighter steering, less bump steer, and less tramlining.
On my own car with stock alignment, I found that with them on the front the steering was fairly light (similar to stock). I was using new Brigestone RE 002's that gave zero tramlining even on bad roads.
 
 
 
 
 
 

Hi M,
 No I don't have any rubbing, guard or strut, but it is close. I have no idea of the car's camber, I suspect it isn't stock but it is not obvious. Seems the guy I bought it from, and many in this thread, arer more interested in getting a  wheel that fits inside the space rather than how well it will work. For me it's function over looks so I would like to put a narrower wheel on the front, as you suggest.
  I just ran your spec through the Wheel and Tire Calculator . http://91mr2.com/wheel-and-tire-calculator and it says your wheels are well in from flush (15mm). Hmm, are you sure cause I am relying on this calculator?  hate it to be wrong.... Perhaps your offset is not 38mm ??? My wheels do not have offset stamped anywhere that I have seen. I measured mine on the ground as 34mm with tyre on. More likely to be 35mm.
I am looking for the exact wheel sizes you have 17/7 & 8, but I think the offset needs to be up near 40mm according to a) that calculator, b) the heaviness I get with 35mm offset (215/40 on 17x8 rim) c) closer to Toyota's setting.  I could be wrong. 
   What size tyres do you have on the front ? and how do you find the steering ?
 
 cheers,
Nigel

Hi Nigel,
 
I must apologise, I said 35 offset in my first sentence, but I meant 32 offset, which is detailed in my second sentence.
 
If you plug in the 32 offset in the calculator, it should be closer to being flush. There is still a very small amount of inside clearance from the original guard.
 
The original front stock wheels that came with the SW20 were 15"x6" JJ 45, so if you go to 7" the offset needs to be adjusted to accomodate for the extra width and clearance from the suspension. It took me months to find a set-up that I was happy with (using the calculator), with the performance and looks as well.
 
I'm an MR2 purist, so I try and keep everything as close to stock as possible. 
 
For my tyres, I am running 215/40 (Kuhmo Ecsta ASX) for the fronts, and 235/40 (Falken Azenis FK453) on the rears.
 
Your next challenge will be to find the same brand of tyres for the staggered set-up, with the correct load rating for the rear.  I am looking at the Yokohama ADVAN AD08 for my next set, once the current set wear out.
 
I have no problems with my steering using the above configuration, and the steering is about the same as when I bought it new. Mind you, I have replaced most of the suspension elements in the car, so I expect it to feel like new !! 
 
As recommended by others on this forum, offsets between 32 and 35 should work fine, but the challenge will be finding a staggered set, that you like, with the same offsets front and rear.  This is why I ended up buying the new Work wheels.
 
Cheers,
M

Firstly thanks @Redtarga,  I missed your post yesterday.  Tyres, pressures etc are fine.
 What I haven't mentioned is that I get pulling L or R when breaking heavily, mainly L. I am pretty sure the steering rods/ends need replacing. This may alter the feel altogether. Tyres, pressures etc are good.
Alignment was done recently when new tyres were fitted, but I am suspicious of the all the moving parts (Ball joints, tie rods, bushes, bearings, etc) and sometimes an alignment can be incorrect due to worn parts. I am getting a report done on all the moving suspension and steering parts, in 2 weeks' time.
 
 Now onto 16" rims, it seems that it may be easier to match up wheels (offsets etc) for the SW20 with 16"s , but I have read that tyre selection is much narrower. I don't know if that means wrong sizes, crap grip or expensive ??  You and Monika have quoted tyre sizes that seem appropriate (205-215 front 235-245 Rear)?
Certainly 17" has a large range.
 
 Do the GTR and GTST wheels look the same ?
 
Thanks Monika also, I may also end up with Work wheels, second hand I'm thinking, will have to see.
 

Performance tyres for 16" wheels:
With tyres for the GTST on the front read my previous post
205/50R16 is readily available in different brands.
 
However there is limited choice for the rears if you want to keep stock rolling diameter.
225/50R16's, are readily available in different brands, but you will have a larger rolling diamater (speedo will read 100kph when you are actually doing 104kph).
With GTR wheels on the rear of an SW20 with 225/50R16's, you will need to roll the fenders slightly if your car is lowered.
The only performance tyre that will give you stock rolling diameter that I know is currently available is the 225/45R16 Yokahama AD08R, but there may be others. 
I currently run those on the rear.
 
 

Seems the rears need more consideration.
I am running 245/40s with 35mm offset currently. While I'm thinking I don't really want to "roll my guards", for all I know they may have already been done. When I got the car it had 255/40s on the back. Oversize for the rims.
 Thanks for the tips, I have some more thinking and researching to do, but will probably come back with
further questions.
 I can't help that think the steering issues I have (probably worn rod ends?) are worsened by running  wheels too far out (big scrub radius). Also I think at least one wheel bearing was fixed prior to sale.
 I imagine that having large scrub radius is like having too much castor, would be trying to rotate both wheels back behind the steering axis, but stopped by the steering linkage.
 I'd like to get a 7" wheel on the front, in close to the strut, to reduce those loads.

To help understand 'scrub radius'
http://www.racecartuner.com/03/307.html
 

Thanks RT, watched it and it is as I thought. The last line says "reduce the scrub as close to zero as possible except on a racing kart".  I believe a few mm helps give the driver feel for traction limit, and currently my offset is 10mm over stock, so I would like to half that, at least, but zero scrub gives no feel, so I've read and believe.

Nigel, suggestion for you.......I don't know where you are in Australia, but if you go to one of the MR2 car meets and see what other people have done, this may allow you to physically inspect their wheel set-ups.  Also, someone may be kind enough to let you have a short drive of their car to see if you like the steering.
 
Hopefully, you'll still find some other MR2 purists around. 
 
Cheers, M

Hi M,
 
 I'm in Berowra, Sydney and your suggestion is good. I didn't know there were MR2 car meets.
 I suppose these get togethers are posted in a forum here somewhere..
 
cheers
Nigel